Throw Out Those 20" Chromies And The 225/35S

[altezzaclub]

http://www.drive.com.au/motor-news/skinny-tyres-the-new-fashion-20141004-10qelg.html?utm_source=outbrain&utm_medium=cpc&utm_campaign=outbrain_amplify

 

Tyre design is blasting back to the future with car makers set to adopt larger diameter wheels with significantly skinnier tyres than most cars are running today.

Despite decades of tyres getting bigger and wider, there is a new trend towards narrower tyres with a large diameter.

The emerging trend towards skinnier tyres is being driven by a desire to reduce fuel use and carbon dioxide emissions.

Tyre companies, including Michelin (pictured) are experimenting with taller, narrower rubber.

"This is the new future," said Damien Hallez, Michelin's head of technical communications. "It helps to improve the energy efficiency [and use less fuel]."

Hallez said every centimetre a tyre increases in diameter there is roughly a 1 per cent reduction in rolling resistance (all things being equal), which is the tyres internal resistance that slows it as it rolls across the ground.

So increasing a tyre's diameter by 2 inches (tyre diameters are measured in inches, not centimetres) would reduce that rolling friction by about 5 per cent.

Having less rubber width also brings improves aerodynamics and further reduces rolling resistance.

"Increasing the diameter we gain in rolling resistance without losing all the security aspects of wet and dry grip," said Hallez.

"There's less deformation of the tyre in the compact patch [the part of the tyre that is touching the road at any time] and less deformation in the side walls so that helps to gain in energy efficiency."

He also said skinnier tyres were better suited to dissipating water, therefore reducing the chance of aquaplaning, or skipping across the surface of the water.

"It's like a boat, it's much more efficient [at going through water]."

Renault design boss Laurens van den Acker agreed wheel and tyre designs would continue to get larger in diameter but with skinnier, more energy efficient tyres.

"It is one of those things that is the best of both worlds," said van den Acker. "The designers want big wheel and the engineers and aerodynamicists want narrow wheels.

"It gives you good comfort, it's good for CO2 … because it has less resistance."

Van den Acker said the only potential negative was in braking performance, something that had to be monitored.

But he said the benefits far outweighed the negatives, particularly when it came to aesthetics.

"If the choice was between having large tyres that are a bit skinny or small tyres that are a bit fat I would still go for the large ones because from the side view it is undoubtedly better," he said.

However, because the skinny tyres are still relatively new – despite being similar widths to tyres sold 40 or 50 years ago – van den Acker said there were issues with supply of replacements.

"What's stopping us is not technology, what's stopping us is tyre manufacturers who are just happy to supply the same tyre and the clients who are feeling more comfortable that the tyre can be bought anywhere, so you have to create a market for these special tyres," said van den Acker.

BMW is one of the first manufacturers to use the new breed of skinny tyres in a production car with its upcoming i3 electric car.

The bulbous carbon-fibre-bodied hatchback gets wheels that are 19 inches in diameter – commensurate to the diameter of wheels used on many performance and luxury cars – but the tyres are almost half as wide as some tyres.

At the front the BMW i3's tyres are just 155mm wide, while the rears are 175mm wide.

By comparison the popular BMW 3-Series has tyres that are between 225mm and 255mm wide, while the Holden Commodore tyres range from 225mm and 275mm.

Various concept cars have also used the larger diameter skinny tyres, while Citroen's C4 Cactus uses 18-inch tyres that are just 155mm wide.

Michelin's Hallez said in many cases the contact patch of rubber on the road was similar to a smaller diameter, wider tyre, so grip levels were often not compromised.

[B-Lugg]

Interesting read.

I would like to see write up from the perspective on safety, sure reducing tyre sizes are great for economy but I'm pretty surprised the decrease to traction and braking aren't present apart from a sentence on aquaplaning.

[altezzaclub]

I don't think they have found a reducton in traction from narrower tyres as they rely on the larger circumferential footprint from a larger tyre So we're working on a similar footprint area but the tyre diameter is larger for a fixed rim size. So new diff ratio needed. I don't think many people suffer from lack of traction normally, but I suppose when its an emergency braking situation it becomes important!

 

What didn't get mentioned was the change in handling from the taller sidewalls flexing, one of the big selling points for low sidewall ratios. The other side of that being a better ride from the tall sidewalls as they soak up the potholes, and tall tyres do more Km than tyres with small sidewalls. Tall tyres soaking up potholes also means far fewer bent rims too.

 

As an aside, I see some tyre pressures are going up with people talking about running 38psi now. That won't help the ride quality!

[B-Lugg]

I should have mentioned specifically in emergency situations.

As you said though with the flew in the larger sidewalls that could also diminish tyre life as well though couldn't it?

 

From my perspective it looks like manufacturers will have to put a lot more money and time in to the design and quality of suspension components to factor in for changes. It makes sense, but sadly I feel new cars now days are absolute rubbish in build quality. I definitely won't be purchasing a near new car any time soon.

[altezzaclub]

manufacturers will have to put a lot more money and time in to the design and quality of suspension components to factor in for changes

 

Yes, as they did to allow for the low profile tyres over the last 20years. Driving 1980 Corollas makes it obvious how much better newer cars ride over sharp bumps in the roads, the spring/shock ratios are quite different. Their suspension has to soak up all the small hard knocks that 70series tyres used to absorb in their sidewalls.

 

Tall sidewalls will make ride comfort easier, but handling aspects will have to change. People will have become used to sharp turn-in & direct steering feel, something that older tall tyres lack. It will get rid of the problem of the wide tyres suffering from negative camber wear though.

[ke70dave]

I suspect they have made some improvements in the tyre compounds in 30years as well.

 

So its likely that you can reduce the width of the tyre and have sufficient grip due to the better tyre compound. A 155 width tyre in an R compound is way grippier than a 235 in china special tyre compound. Hopefully they have also sorted out how to make tyres last longer with good compound, else you will be replacing the skinny tyres more often.....further driving up the cost of owning a new car.